Edexcel International GCSE Chemistry
Edexcel International GCSE Chemistry Section 4: Organic Chemistry Exam Questions
Free Edexcel International GCSE Chemistry exam questions for Section 4: Organic Chemistry, with a mark scheme for every pack. Covers naming and formulae, homologous series, isomers, crude oil and cracking, alkanes, alkenes, alcohols, carboxylic acids, esters and synthetic polymers.
Section 4: Organic Chemistry exam questions
3 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About Edexcel International GCSE Chemistry Section 4: Organic Chemistry
Section 4 of Edexcel International GCSE Chemistry (4CH1) covers carbon compounds. You learn how to represent organic molecules using general, molecular, structural and displayed formulae, name compounds, and identify structural isomers. You then study crude oil, fractional distillation and cracking, the reactions of alkanes and alkenes, and the chemistry of alcohols, carboxylic acids and esters, before finishing with addition and condensation polymers. It is assessed on both papers, with bold content (including much of the alcohols, carboxylic acids, esters and condensation polymers) on Paper 2 only. Drawing displayed formulae, naming isomers and writing equations are core exam skills.
What you need to know
- Introduction A homologous series has the same general formula, similar chemical properties, a gradual change in physical properties and differs by CH2. Learn functional groups, naming up to six carbons, structural isomers and reaction types: addition, substitution and combustion.
- Crude oil Crude oil is a mixture of hydrocarbons separated by fractional distillation into refinery gases, gasoline, kerosene, diesel, fuel oil and bitumen. Longer chains have higher boiling points and viscosity and are less easily ignited. Incomplete combustion gives toxic carbon monoxide; sulfur dioxide and oxides of nitrogen cause acid rain. Cracking uses silica or alumina catalyst at 600 to 700 °C.
- Alkanes Saturated hydrocarbons, general formula CnH2n+2. They react with bromine in the presence of ultraviolet light by substitution, for example CH4 + Br2 → CH3Br + HBr.
- Alkenes Unsaturated hydrocarbons with C=C, general formula CnH2n. They decolourise bromine water (orange to colourless) by addition.
- Alcohols Functional group -OH. Ethanol can be oxidised to ethanoic acid (for example by acidified potassium dichromate) and burns in air. It is manufactured by hydration of ethene with steam (about 300 °C, 60 to 70 atm, phosphoric acid catalyst) or by fermentation of glucose with yeast at about 30 °C without oxygen; compare the two methods.
- Carboxylic acids and esters Carboxylic acids contain -COOH, react with metals and carbonates like other acids and are weak acids. An alcohol and a carboxylic acid react with an acid catalyst to form an ester, for example ethyl ethanoate, used in food flavourings and perfumes.
- Synthetic polymers Addition polymers such as poly(ethene), poly(propene) and poly(chloroethene) form from alkenes; they are inert and non-biodegradable, causing disposal problems. Condensation polymers such as polyesters form from a dicarboxylic acid and a diol, releasing water; some polyesters are biodegradable.
Common mistakes in Section 4: Organic Chemistry
- Drawing isomers that are actually the same molecule, for example a bent chain that is just a rotated straight chain.
- Saying alkanes react with bromine water like alkenes. Alkanes only react with bromine by substitution in UV light.
- Leaving the C=C in an addition polymer repeating unit.
- Mixing up the conditions for fermentation and hydration of ethene.
- Naming esters with the acid part first. The alcohol part comes first: ethanol plus ethanoic acid gives ethyl ethanoate.
Try three Section 4: Organic Chemistry exam-style questions
1. A hydrocarbon contains 85.7% carbon and 14.3% hydrogen by mass. Calculate its empirical formula. (3 marks)
Show the mark scheme answer
C: 85.7 / 12 = 7.14; H: 14.3 / 1 = 14.3; ratio 1 : 2, so CH2.
2. Draw or describe the displayed formulae of two structural isomers of C4H10 and name them. (3 marks)
Show the mark scheme answer
Butane: straight chain of four carbons; methylpropane (2-methylpropane): three-carbon chain with a CH3 on the middle carbon; both with all H atoms shown and correct bonding.
3. Give one advantage and one disadvantage of making ethanol by fermentation compared with hydration of ethene. (2 marks)
Show the mark scheme answer
Advantage: uses a renewable raw material (sugar from plants), or low temperature so less energy; disadvantage: slow (batch) process, or produces impure, dilute ethanol needing distillation.
Section 4: Organic Chemistry FAQs
What does Edexcel International GCSE Chemistry Section 4 cover?
It covers naming and formulae of organic compounds, isomers, crude oil and cracking, alkanes, alkenes, alcohols, carboxylic acids, esters and synthetic polymers.
Which paper is Section 4 on?
Section 4 is assessed on both Paper 1 and Paper 2, with content shown in bold in the specification assessed on Paper 2 only.
How should I revise organic chemistry for 4CH1?
Make a summary sheet for each homologous series with its general formula, functional group, first few names and key reactions with conditions. Practise drawing displayed formulae and isomers until you can do them quickly.
